Anatomy and Physiology: Chapter 3 - Energy, Chemical Reactions, & Cellular Respiration
Describe two models of enzyme action
- "Lock and key" Theory: In this analogy, the lock is the enzyme and the key is the substrate. Only the correctly sized key (substrate) fits into the key hole (active site) of the lock (enzyme). - "Induced Fit" Theory: The induced-fit theory assumes that the substrate plays a role in determining the final shape of the enzyme and that the enzyme is partially flexible.
What is energy?
- Capacity to do work - Exists in two states i. Potential energy = stored energy (energy of position) ii. Kinetic energy = energy of motion - Potential energy must be converted to kinetic energy before it can do work
How is a cofactor different from a coenzyme? Why are either of these needed?
- Cofactor: An inorganic ion that is weakly bound to an enzyme and required for its activity. - Coenzyme: A nonprotein organic molecule that plays a role in catalysis by an enzyme Coenzymes transport molecules.
List methods of controlling the activity of enzymes
- Competitive Inhibition - Noncompetitive Inhibition
Describe two ways in which a defective enzyme could cause disease
- Defective enzymes cannot follow a specific pathway - leading to disease. - Defective enzyme cannot follow a specific pathway leading the enzyme to follow a different pathway, causing the overproduction - leading to disease.
Describe the different types of chemical reactions (hydrolysis, dehydration synthesis [condensation], exchange reactions, reversible, irreversible).
- Hydrolysis: Chemical process in which a molecule of water is added to a substance. Sometimes this addition causes both substance and water molecule to split into two parts. In such reactions, one fragment of the target molecule (or parent molecule) gains a hydrogen ion. - Dehydration Synthesis (condensation): The process of joining two molecules, or compounds, together following the removal of water. - Exchange reactions: Atoms, molecule, ions, or electrons are exchanged between two chemical structures. - Reversible reactions: Reactants become products at a rate equal to products becoming reactants; no net change in concentration. - Irreversible reactions: Reactants converted to product at a rate that yields a net loss of reactants and a net gain in products.
How is a metabolic pathway different from a multienzyme complex?
- Metabolic pathway: A series of steps in which a specific molecule is altered in each step in order to form a specific product. A specific enzyme catalyzes each step of the pathway. - Multienzyme complex: A team of enzymes for several steps of a metabolic pathway. The product from the first reaction can then pass quickly to the next enzyme until the final product is released.
What is metabolism? Catabolism? Anabolism?
- Metabolism: A collection of controlled biochemical reactions that take place within cells of an organism. - Catabolism: The breakdown of complex organic molecules into simpler ones. Reactions are called catabolic or degradative reactions, they are usually hydrolytic reaction and are exergonic. - Anabolism: The buildup of complex organic molecules from simpler ones, reactions are called anabolic or biosynthetic. They involve dehydration synthesis (release water) and are endergonic.
List the steps of cellular respiration
- The first stage of cellular respiration is glycolysis. It takes place in the cytosol of the cytoplasm. Glycolysis means "glucose splitting". Enzymes split a molecule of glucose into two molecules of pyruvate. - In stage two, the pyruvate molecules are transported into the mitochondria. The mitochondria are the organelles known as the energy "powerhouses" of the cells (Figure below). In the mitochondria, the pyruvate, which have been converted into a 2-carbon molecule, enter the Krebs cycle. Notice that mitochondria have an inner membrane with many folds, called cristae. These cristae greatly increase the membrane surface area where many of the cellular respiration reactions take place. - In stage three, the energy in the energy carriers enters an electron transport chain. During this step, this energy is used to produce ATP.
What are the primary gains from the Kreb's cycle?
2 ATP
What are the net gains from the intermediate stage?
2 CO2 molecules, 2 NADH+H molecules, and 2 Acetyl CoA molecules
Name the primary gains from the process of glycolysis
2 pyruvate, 2 ATP, 2 NADH
How many ATPs are made through the electron transport chain?
34 ATP and H20
Compare a competitive inhibitor and a noncompetitive inhibitor
A competitive inhibitor will block the enzyme's active site, while a noncompetitive inhibitor will bind to the enzyme somewhere other than the active site of the enzyme; an allosteric site.
What is a metabolic pathway?
A series of chemical reactions, all involving enzymes and energy, beginning with reactants or substrates and ending with products.
What is cellular respiration?
ATP Production
What is the difference between an enzyme active site and an allosteric site?
Active site: A specific area of an enzyme where the substrate binds to the enzyme. Allosteric site: A site other than the active site.
Compare anaerobic and aerobic cellular respiration
Aerobic respiration takes place in the presence of oxygen, while anaerobic respiration takes place when no oxygen is present.
How are enzymes affected by temperature and pH?
As the temperature increases, so does the rate of reaction. But very high temperatures denature enzymes. Changes in pH may not only affect the shape of an enzyme but it may also change the shape or charge properties of the substrate so that either substrate cannot bind to the active site or it cannot undergo catalysis.
Which organ uses almost solely glucose for energy production?
Brain
What is the first reaction of the Kreb's cycle?
Citric Acid
Where does glycolysis occur?
Cytosol - Cytoplasm
Describe the saturation of an enzyme. How does saturation affect enzymatic activity rate?
During saturation at particular concentration of enzyme and at a particular concentration of substrate, all the enzymes molecules get engaged with substrate and no more free enzymes available for any further substrate for binding, at this point the enzyme is termed to be saturated.
Which type(s) of chemical reactions are endergonic? Exergonic?
Endergonic: Catabolic reactions Exergonic: Anabolic reactions
Why are enzymes needed in our cells?
Enzymes are proteins that control the speed of chemical reactions in your body. Without enzymes, these reactions would take place too slowly to keep you alive. Some enzymes, like the ones in your gut, break down large molecules into smaller ones.
How does an enzyme decrease activation energy?
Enzymes lower the activation energy of a reaction by binding one of the reactants, called a substrate, and holding it in a way that lowers the activation energy.
Overall, is glycolysis endergonic or exergonic?
Exergonic reaction
What two tissues are involved in the Cori cycle?
Extrahepatic tissues and the liver
What molecules enter and exit the intermediate stage?
In: 2 pyruvic acid molecules Out: 2 CO2 molecules, 2 NADH+H molecules, and 2 Acetyl CoA molecules
What is the function of NADH?
It is used it the citric acid cycle to transport electrons across the mitochondrial membrane. The electrons flow through 4 complexes, each of which pumps protons into the intermembrane space. This H+ gradient is then used to drive ATP synthase, which pumps out one ATP per 4H+
Compare and list examples of kinetic and potential energy
Kinetic energy is energy of motion, while potential energy is stored energy. Examples of Kinetic Energy: Moving a skateboard, A basketball passing through the hoop, and a person climbing a ladder. Examples of Potential Energy: A rock at the edge of a cliff
What mechanism takes over if an adequate supply of oxygen is not available?
Lactic Acid Fermentation
Explain the law of mass action
Law of mass action: Law stating that the rate of any chemical reaction is proportional to the product of the masses of the reacting substances, with each mass raised to a power equal to the coefficient that occurs in the chemical equation.
How is a metabolic pathway different from a metabolic web?
Metabolic Web doesn't just get energy from glucose - can also break down fat for energy.
Where does the intermediate stage occur?
Mitochondria
Explain the role of oxygen in the electron transport chain
Oxygen acts as the final electron acceptor at the end of the electron transport chain.
What molecule is described as the final electron acceptor? Why?
Oxygen, because molecular oxygen is a highly oxidizing agent and, therefore, is an excellent acceptor.
What is an enzyme?
Proteins that speed up reactions by reducing the activation energy without being consumed in the reaction.
Describe the processes that make up the Cori cycle
The "cori cycle" is the metabolic pathway in which lactate (having been produced by anaerobic glycolysis in the muscles) moves to the liver wherein it is converted into glucose.
Define activation energy
The amount of energy required to cause a chemical reaction; specifically the energy required to reach the transition state.
What is an oxygen debt?
The amount of extra oxygen required by muscle tissue to oxidize lactic acid and replenish depleted ATP and phosphocreatine following vigorous exercise.
Describe the chemiosmotic theory
The chemiosmotic hypothesis suggests that the action of ATP synthase is coupled with that of a proton gradient. It is the action of the proton gradient that causes a proton motive force that allows ATP synthase to phosphorylate ADP and inorganic phosphate to ATP.
How does the electron transport chain create a proton gradient?
The electron transport chain creates the proton gradient. When some members of the chain pass electrons, they also accept and release protons, which are pumped into the intermembrane space at three points. The resulting proton gradient stores potential energy, referred to as the proton-motive force.
What is glycolysis?
The first step in the breakdown of glucose to extract energy for cellular metabolism.
What do we use the proton gradient for?
The proton gradient can be used as intermediate energy storage for heat production and flagellar rotation. In addition, it is an interconvertible form of energy in active transport, electron potential generation, NADPH synthesis, and ATP synthesis/hydrolysis.
What is a substrate?
The reactant that binds to the enzyme's active site and is transformed into product.
What happens to the NADH and FADH2 when they arrive at the electron transport chain?
The role of NADH and FADH2 is to donate electrons to the electron transport chain. They both donate electrons by providing an hydrogen molecule to the oxygen molecule to create water during the electron transport chain.
